Sailboat having side keels



March 1, 1955 M. F. HILL SAILBOAT HAVING SIDE KEELS Filed May 15 1951 FIGJ- 2 Sheets-Sheet 1 FIGIII 25 36 INVENToR.

M. F. HILL March 1, 1955 SAILBOAT HAVING SIDE KEELS Y 2 Sheets-Sheet 2 Filed May 15 1951 oINVEN TOR HQE United States Patente-O This. application is a continuation in part of my copending application Serial No. 112539501, filed November T, 1949, now abandoned.

This invention relates to the use of side keels with shallow draft lightly constructed boats.

One of the objects of my invention is to replace the usual deep heavy ballasted keel of a sail boat by substituting two side keels which draw little Water when the mast is vertical.

Another object of my invention is to set each keel at such an angle to the vertical line of the mast that the keel acting as the lee keel will become substantially vertical when the boat is heeled over during sailing.

A further object of my invention is to take advantage of the shift of the center of buoyancy to leeward to increase the moment arm of the Windward side keel and decrease the moment arm of the leeward side keel so as tolcounterbalance the thrust of the Wind against the sa1s.

A still further object of my invention is to provide relatively light weight side keels which will be as effective in counter-balancing wind pressures as the usual deep heavily ballasted central keel.

Another object of my invention is to provide a truss from one side of the boat to the other to take the stresses of wind and Water as well as the weight of the side keels.

In the drawings:

Fig. I is a plan view of my boat with the side keels.

Fig. II is a partial section on line II--II in Fig. I.

Fig. III is a section on line III- III in Fig. II showing the truss and side keels.

Fig. IV is a partial plan view of the boat With the deck, side keels and inwale removed to show the transverse frames and the top member of the truss.

Fig. V shows how the sides of the boat are shaped.

Fig. VI shows how the bottom of the boat is shaped.

Fig. VII is a side elevation showing the mast, stay and shroud connections.

Fig. VIII shows how the lee keel becomes vertical when the boat is heeled over and the Windward keel rises out of water.

Fig. IX is a section on line IX--IX thru the rudder box in Fig. I.

Fig. X is a plan view of the rudder box alone.

Fig. XI is a section on line XI-XI in Fig. X.

Fig. XII shows an elevation of a preformed cross frame.

Fig. XIII shows a detail of a hull joint.

In the embodiment of my invention the sides 9 and 10 and bottom 18 are joined together to form a boat. End members 34 (one of which is shown in Fig. II) close the ends of the hull. The boat may have one or more transverse frames 21 and 23 (Figs. IV and XII) and a deck 1 with coaming 45 around the cockpit as shown in Fig. I. The boat is described in detail in my eopending application Ser. No. 226,498.

Fig. III shows a truss 29 fitted between the sides, bottom and deck of the boat. This truss 29 serves to take the stresses of the wind, mast, and water thrusts on the side keels 37 and 38 and to relieve the hull of the greater part of such stresses transverse to the longitudinal center line of the boat. It is bolted thru the sides 9 and 10 to the brace arms 35 and 36 of the side keels 37 and 38 at 32 and 33 respectively. The truss 29 may have a step, socket, or tube 39 to receive the mast 40. It also has an upper truss member 41 under the deck 1 (Figs. III

and I). This member 41 may be bolted thru the deck 1` 8 2,703,064 Patented Mar. l, 1955 v ICC tothe tension anns 43' and 44' extending inwardl fromf the side keels, 3 7` and 38 respectively. Ther tension arrns- 43 and 44- and brace arms 35 and 36 `may be welded` to their respective steel. side keels 37 and 38.

These sidey keels extend outward and downward from the Vull ata predetermined angle so thatunder average sailing. conditions of wind and Weather the,4 side keel acting as the lee keel will become Substantially vertical in the water.

In the bo'at described in my Copending application Ser. No. 226,498 these side keels were made of'one. .half inch thick steel plates and weighed 10ft) lbs. each. They extended just; enough below the bottom ofv the boatY to keep it olf the ground when it was pulled up onv shore.v

When the boat heels over d ue to wind pressure on the sail as indicated by the arrow' inFig.. VIII, the center of buoyancy will shift from the middle of.` the boat to some position as 6.6. Thedstar-board or Windward keelwill lift out of water and be further away from 66 so that its moment arm will increase to the length shown by the double pointed arrow 67. At the same time the moment arm of the lee keel will decrease to the length indicated by the double pointed arrow 68. It is the increase of the Windward moment arm of the Windward side keel and the decrease of the leeward moment arm of the leeward side keel which makes my side keels so effective. The fact that the lee keel becomes more and more vertical to the surface of the water makes it increasingly more effective as the boat heels over is another factor in making my side keels so effective.

In the hull and side keel proportions used in my copending application Ser. No. 226,498 the distance of the center of buoyancy at 66 (when the boat was heeled over as in Fig. VIII) was about 5 feet from the center of gravity of the Windward side keel 38. Since 38 weighed lbs. its counterbalancing effect was 500 ft. lbs. At the same time the distance of the center of gravity of the lee side keel from the center of buoyancy at 66 was shortened to 2 feet so that its downward pull was 200 ft. lbs. The net counterbalancing effect was 500 ft. lbs-200 ft. lbs. or 300 ft. lbs. In addition to this was the weight of the hull which was about lbs. The center of gravity of the hull from the center of buoyancy at 66 was 1 and 1/2 feet to Windward. Therefore the weight of the hull helped the counterbalancing to the extent of another 210 ft. lbs. making a total of 510 ft. lbs.

Had this boat had only one centrally located keel as indicated by the dashed line 72 in Fig. VIII it would have been only 18 inches away from the center of buoyancy at 66 and would have had to Weigh 340 lbs.

Since the total weight of my side keels was only 200 pounds there was a saving in weight of 140 lbs. This is very important in small lightly built boats.

In my boat I fastened the lower end of the side stays 40A in Fig. VII to the side keels. By doing this the side keels and truss 29 took most of the sailing stresses, and my hull could be made of lighter material.

This saving in Weight of keels and hull is Very important in small boats built by amateurs. The deep heavily ballasted keel is very diicult if not impossible for an amateur builder to make. Side keels of sheet steel can be made and cut to shape by almost any steel supply house. Since each side keel weighs only 100 lbs. it can be easily made, attached or detached and is easy to handle.

The boat can be transported from harbor to harbor on smaller and lighter trailers.

I do not limit the use of my side keels to the particular hull shown in the drawings. They may be used with many types of shallow draft hulls.

What I claim is:

l. In the hull of a sailing yacht, side and bottom members, frame members across said hull secured to said side and bottom members fixing their iiare, side plates therefore, one on each side of said hull, sloping outward and downward to approach a vertical position in the Water as the hull heels, rigging for said hull subject to stresses of wind pressure causing heeling While sailing, a truss fastened across said hull amidships between said side members, said side plates being fastened to said truss and thereby to each other, a mast socket on said w truss, and braces and tension arms on said plates fastened to said truss.

2. In combination a hull of a shallow draft sailboat, cross members in said hull fastened between the deck, sides, and bottom of said hull, rigging including mast, stays, and shrouds, and sails subject to wind pressures while sailing, a side keel on each side of said hull sloping outward and downward at an angle to said mast, at least one of said cross members acting as a truss and fastened through the hull to said side keels to relieve the hull of most sailing stresses, said angle to the mast of each side keel being such that when acting as a lee keel it will become more and more vertical to the surface of the water during average sailing conditions, said hull having its center of buoyancy shift substantially to leeward as said hull heels over, having the moment arm of said side keel acting as a Windward keel increase in length while the moment arm of said side keel acting as a lee side keel will decrease in length, and having said side keels having substantial weight with relation to said hull.

3. The combination claimed in claim 2 and having the side stays of said mast fastened to said side keels.

References Cited in the le of this patent UNITED STATES PATENTS 

